Welding control systems have taken a wide variety of different forms. Many systems have been employed to monitor the current or voltage and utilize this data to provide signals which are included in a feedback network to control the welding operation.
Also, individual parameters, such as current, voltage and travel speeds have been used to provide an average value of heat input. This technique, however, produces an after-the-fact control signal and does not permit change of in-process heat inputs to maintain a standard level of heat input.
It is important in many cases to provide a constant heat input for a welding operation. An example of the importance of maintaining a constant heat input to an arc welding operation is in the manufacture of a truck wheel. In this operation, a disc involving a relatively thin cold material is welded to a relatively thick rim which is generally a hot rolled material. In such arc welding of wheels, it is important to provide precise heat inputs to establish minimum weld penetration and heat input while preserving the strength in the cold work disc by minimal annealing in the heat affected zone.